From the invoices page, choose the invoice you want to send and click on the view button to open the invoice builder.
Click on the top-left button "Send"
In the pop-up, fill in the email and subject or keep the default ones, add your notes, and click on "Send".
An email will send automatically to your customer with the invoice link and notes if applicable.
You will receive an email notification when the recipient opens your email the first time, you can also check the tracking details any time by clicking on the check button.